The present invention relates generally to quantifying the relative benefits of different scenarios of operating and designing an equipment module and, more particularly, to systems and methods for quantifying the relative benefits of designing and operating an equipment module in accordance with an xe2x80x9coperate to failure approach,xe2x80x9d a xe2x80x9cprognostic approach,xe2x80x9d and a xe2x80x9cmaintenance approach,xe2x80x9d as well as quantifying the benefits of varying other aspects relevant to the operation and design of the equipment module.
It is common for equipment modules to be designed and operated according to different scenarios. For example, it is conventional for an equipment module, which may be an individual component, a component within a system, or a system of components, to be designed and operated in accordance with one of an xe2x80x9coperate to failure approach,xe2x80x9d a xe2x80x9cprognostic approach,xe2x80x9d or a xe2x80x9cmaintenance approach.
The maintenance approach refers to a process of replacing or servicing an equipment module at a scheduled interval, such as an interval based on hours of use. The goal of the maintenance approach is to schedule maintenance intervals so that equipment modules are serviced or replaced before they fail, so that failure is avoided. If maintenance intervals are scheduled too frequently, the benefits resulting from the performed maintenance may be offset by excessive maintenance expenses. If maintenance intervals are not scheduled frequent enough, the benefits resulting from the performed maintenance may be offset by excessive failures of equipment modules.
The prognostic approach refers to a process of prognosticating (that is, using present indications as a guide) to predict a failure in advance. The prognostic approach typically requires monitoring of characteristics of the equipment module that can provide an indication of an impending problem with the equipment module. In some cases the equipment module must be designed in a manner that facilitates the monitoring of the characteristic(s) that are of interest. The goal of the prognostic approach depends upon the equipment module of interest. The goal may be to replace an equipment module just prior to a predicted failure of that equipment module. Alternatively, the goal may be to replace or service an equipment module just prior to the equipment module being degraded to a point at which the cost of the replacement or servicing becomes excessive. If too much effort is put into a prognostic approach, the benefits resulting therefrom may be offset or outweighed by excessive expenses associated with the prognosticating. If insufficient efforts are put into a prognostic approach, then the benefits resulting therefrom may be offset or outweighed by excessive failures of equipment modules.
The operate to failure approach refers to operating an equipment module until failure, without using the maintenance approach or the prognostic approach. The equipment module is replaced after it fails.
Numerous decisions that will impact the operation of an equipment module are made during the course of designing the equipment module. For example, it is common for spare equipment modules to be designed into a system. A spare equipment module is typically redundant to a non-spare equipment module and is operative to function in a manner so as to xe2x80x9cback upxe2x80x9d or operate in the place of the non-spare equipment module when the non-spare equipment module becomes inoperative.
Whereas the general concepts of the operate to failure approach, the prognostic approach, and the maintenance approach are well known, and it is known to prolong operation of a system such as by incorporating spares into the system, a problem exists because it can be difficult to select between these scenarios when designing or operating an equipment module. It can be difficult to quantify the relative benefits of these scenarios because numerous factors must be taken into consideration. For example, different equipment modules have numerous characteristics and associated costs that should be considered. As a result, designers and operators of equipment modules often do not optimally select from the operate to failure approach, the prognostic approach, the maintenance approach or other scenarios, such that it is common for the design and operation of equipment modules to be less than optimal.
The present invention solves the above problems, and other problems, by providing systems and methods for quantifying the relative benefits of different scenarios of operating and designing equipment modules. More specifically, the present invention provides, in various combinations, systems and methods for quantifying the relative benefits of designing and operating an equipment module or system in accordance with the operate to failure approach, the prognostic approach, and the maintenance approach, as well as quantifying the benefits of other scenarios, such as incorporating different numbers of spare equipment modules into a system.
In accordance with one aspect of the present invention, an equipment module is analyzed through the use of an array of failure probability values, which can more specifically be in the form of a failure probability curve. The array of failure probability values provides an indication of the probability that the equipment module will fail at a plurality of different times. A cost of operating the equipment module is determined by calculating the cost of operating the equipment module at each of the different times using the array of failure probability values, so that the cost calculated at each of the different times is proportional to the probability that the equipment module will fail at the respective time.
In accordance with another aspect of the present invention, the cost of operating the equipment module at each of the different times includes a recurring cost value and a non-recurring cost value. The recurring cost value can include, but is not limited to, the cost of the equipment module, costs incurred due to failure of the equipment module, costs of prognostic hardware for the equipment module, and costs of prognostic procedures for the equipment module. The non-recurring cost value can include, but is not limited to, the costs of designing prognostic capabilities into the equipment module.
In accordance with another aspect of the present invention, at least one additional probability is utilized when calculating the cost of operating the equipment module. The additional probability can include, but is not limited to, a probability that the equipment module will be incorrectly identified as needing to be refurbished, a probability that the equipment module will be incorrectly identified as needing to be replaced, a probability that no notification of a necessary refurbishment will be provided for the equipment module, such that the equipment module fails without warning, and a probability that no notification of a necessary replacement will be provided for the equipment module, such that the equipment module fails without warning.
In accordance with another aspect of the present invention, a maintenance time indicates a time at which maintenance should be performed on the equipment module. The plurality of different times is a series of times that are designated as a first time through a last time, respectively, and the maintenance time is between the first time and the last time. Additionally, the calculated costs are a series of first costs designated as a first cost through a last cost. The series of costs respectively correspond to the series of times, and the costs are calculated so that at least some of the costs, which correspond to times after the maintenance time, are proportional to probabilities, which are provided by the array of failure probability values, that correspond to times prior to the maintenance time.
In accordance with another aspect of the present invention, the different times are a series of times, so that the calculated costs are a series of first costs that correspond to the series of times. Further, the maintenance time for the equipment module is identified by calculating a series of second costs that respectively correspond to the series of times. Each second cost is calculated by dividing a respective sum by the respective time corresponding to the second cost. For each second cost, the respective sum includes at least the first cost that corresponds to the respective time of the second cost. The maintenance time is the time of the series of times that corresponds to the smallest second cost of the series of second costs.
In accordance with another aspect of the present invention, different first and second scenarios of operating the equipment module are specified. The cost of operating the equipment module in accordance with the first and second scenarios are determined in the manner described above. Thereafter, the difference between the cost of operating the equipment module in accordance with the first and second scenarios is determined. The first and second scenarios can be selected from a group consisting of an operate to failure approach, a prognostic approach, and a maintenance approach. Alternatively, the first and second scenarios are defined by at least one variable, and the specifying of the first scenario comprises specifying a first value for the variable and the specifying of the second scenario comprises specifying a second value for the variable that is different from the first value. The variable can be, but is not limited to, the cost of the equipment module, costs incurred due to failure of the equipment module, the number of equipment modules, the total amount of time that a system incorporating the equipment module is expected to operate in the entire life of the system, the average length of time that the system incorporating the equipment module operates, wherein the system operates intermittently, the total number of the systems that will be produced, the cost of prognostic hardware for the equipment module, the cost of prognostic procedures for the equipment module, the cost of designing prognostic capabilities into the equipment module, a probability that the equipment module will be incorrectly identified as needing to be refurbished, a probability that the equipment module will be incorrectly identified as needing to be replaced, a probability that no notification of a necessary refurbishment will be provided for the equipment module, such that the equipment module fails without warning, and a probability that no notification of a necessary replacement will be provided for the equipment module, such that the equipment module fails without warning.
In accordance with another aspect of the present invention, in addition to calculating the costs for a first and second scenario, the costs are also calculated for second and third scenarios. A first value is determined that quantifies the difference between the cost of operating the equipment module in accordance with the first scenario and the cost of operating the equipment module in accordance with the second scenario, a second value is determined that quantifies the difference between the cost of operating the equipment module in accordance with the third scenario and the cost of operating the equipment module in accordance with the fourth scenario, and the difference between the first and second values is quantified.
In accordance with another aspect of the present invention, a program module is operative to perform the methods of the present invention when executed by a computer.
The present invention advantageously facilitates the selection between numerous scenarios for designing and operating an equipment module by quantifying the relative benefits of the scenarios.